1. Field of the Invention
The present invention relates to gas-flow measuring instruments for measuring a gas flow of intake gas, and in particular relates to a gas-flow measuring instrument for mainly measuring a gas flow in an intake gas passage for sucking gas.
2. Description of the Related Art
Although there are no publicly known examples describing the reduction in an effect of water splashes on a flow measuring element, which is a main object of the present invention, conventional techniques, which are similar to the present invention, directed to isolating foreign materials using an inertial force of a foreign material contained in intake gas are as follows.
(1) Japanese Publication of Unexamined Patent Application No. 11-248505 discloses that a bypass passage is divided into two and a flow measuring element is arranged in a first bypass passage. Dust breaking into the bypass passage is directed and isolated to a second bypass passage opened in a velocity vector direction. However, by construction, the mainstream of air flowing through the bypass passage becomes the second bypass passage, in which the flow measuring element is not arranged, so that a sufficiently stable airflow cannot be obtained in the first bypass passage, and there is a problem that flow measuring accuracies are deteriorated to a large extent.